title: The mobility of two kinase domains in the Escherichia coli chemoreceptor array varies with signalling state.
abstract: Motile bacteria sense their physical and chemical environment through highly cooperative, ordered arrays of chemoreceptors. These signalling complexes phosphorylate a response regulator which in turn governs flagellar motor reversals, driving cells towards favourable environments. The structural changes that translate chemoeffector binding into the appropriate kinase output are not known. Here, we apply high-resolution electron cryotomography to visualize mutant chemoreceptor signalling arrays in well-defined kinase activity states. The arrays were well ordered in all signalling states, with no discernible differences in receptor conformation at 2-3 nm resolution. Differences were observed, however, in a keel-like density that we identify here as CheA kinase domains P1 and P2, the phosphorylation site domain and the binding domain for response regulator target proteins. Mutant receptor arrays with high kinase activities all exhibited small keels and high proteolysis susceptibility, indicative of mobile P1 and P2 domains. In contrast, arrays in kinase-off signalling states exhibited a range of keel sizes. These findings confirm that chemoreceptor arrays do not undergo large structural changes during signalling, and suggest instead that kinase activity is modulated at least in part by changes in the mobility of key domains.
authors.affiliation: California Institute of Technology, 1200 E. California Blvd, Pasadena, CA, 91125, USA.
authors.forename: Ariane
authors.initials: A
authors.lastname: Briegel
authors.forename: Peter
authors.initials: P
authors.lastname: Ames
authors.forename: James C
authors.initials: JC
authors.lastname: Gumbart
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Oikonomou
authors.forename: John S
authors.initials: JS
authors.lastname: Parkinson
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D055032:Electron Microscope Tomography; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D000071677:Histidine Kinase; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D000072236:Methyl-Accepting Chemotaxis Proteins; D008954:Models, Biological; D008958:Models, Molecular; D011487:Protein Conformation; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D000071677:Histidine Kinase; C000607608:cheA protein, E coli